Spandex of a particular composition and process for making same

ABSTRACT

The invention provides spandex having improved hysteresis and a method for making such spandex. The spandex of the invention comprises the polyurethaneurea reaction product of: (a) poly(tetramethylene ether) glycol (b) 1-isocyanato-4-[(4-isocyanatophenyl)methyl]benzene wherein the mole ratio of diisocyanate to glycol is from about 1.52 to about 2.04; and (c) a mixture of chain extenders comprising: from about 35 to about 55 mole percent ethylene diamine; and from about 45 to about 65 mole percent 1,2-propanediamine.

CONTINUITY DATA

This application is a divisional of U.S. patent application Ser. No.10/264,742, filed Oct. 4, 2002, now pending.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to spandex comprising a particularcomposition, especially a polyurethaneurea spandex made with aparticular combination of diamine chain extenders.

2. Description of Background Art

A variety of compositions for polyurethaneurea spandex have beendisclosed, for example in U.S. Pat. Nos. 5,981,686, 6,403,216, and5,000,899 and in Japanese Published Patent Applications JP03-279415 andJP58-194915. However, such compositions can have high hysteresis and canform unstable solutions.

An improved composition for polyurethaneurea spandex is still needed.

SUMMARY OF THE INVENTION

The present invention provides a spandex comprising the polyurethaneureareaction product of poly(tetramethylene ether) glycol,1-isocyanato-4-[(4-isocyanatophenyl)methyl]benzene wherein the moleratio of diisocyanate to glycol is at least about 1.52 and the moleratio of diisocyanate to glycol is at most about 2.04, and a mixture ofchain extenders comprising:

from about 35 mole to about 55 mole percent ethylene diamine; and

from about 45 mole percent 1,2-propanediamineto about 65 mole percent1,2-propanediamine.

The invention also provides a process for making such a spandex.

BRIEF DESCRIPTION OF THE FIGURE

FIG. 1 presents the effect on polyurethaneurea solution viscosity of theamount of 1,2-propanediamine in the mixture of chain extenders.

DETAILED DESCRIPTION OF THE INVENTION

It has now been found that spandex comprising a particular compositionof polyurethaneurea has unexpectedly low hysteresis and that thepolyurethaneurea has unexpectedly good solution viscosity stability. Theterm “hysteresis” as used herein means the difference between load powerand unload power. Such spandex can be used in woven, knit, and nonwovenfabrics, and can provide stretch and recovery in personal care articlessuch as diapers.

As used herein, spandex means a manufactured fiber in which thefiber-forming substance is a long chain synthetic polymer comprised ofat least 85% by weight of a segmented polyurethane.

The spandex of the invention comprises the polyurethaneurea reactionproduct of poly(tetramethylene ether) glycol,1-isocyanato-4-[(4-isocyanatophenyl)methyl]benzene, and a mixture ofchain extenders comprising about 35 to 55 mole percent ethylene diamineand about 45 to 65 mole percent 1,2-propanediamine, typically about 40to 50 mole percent ethylene diamine and about 50 to 60 mole percent1,2-propanediamine. The mole ratio of diisocyanate to polymeric glycol(the “capping ratio”) can be about 1.52 to 2.04. When the1,2-propanediamine content and/or the ratio of diisocyanate to glycolare higher, load power and hysteresis can be undesirably increased. Whenthe 1,2-propanediamine content is too low, the viscosity stability ofsolutions of such polyurethaneurea can suffer.

The poly(tetramethylene ether) glycol can have a number averagemolecular weight of about 1600 to 2500 daltons. The glycol can containacids, acid-producing compounds, or catalysts, which can be added beforethe capping step, for example 10 to 100 parts per million based onpolymeric glycol weight of phosphoric acid esters, phosphoric acid,benzenesulfonic acid, p-toluenesulfonic acid, sulfuric acid, stannousoctoate, alkyl titanates, and the like. It is unnecessary to include, inthe polymeric glycol, diols having a low molecular weight below about250 Daltons, such as butanediol, hexanediol, 1,4-cyclohexanedimethanol,and the like, and the polymeric glycol can be substantially free of suchdiols, meaning less than about 5 mole percent of such diols can bepresent.

To control polyurethaneurea molecular weight, at least onemonofunctional chain terminator can be used, for example diethylamine,di-n-butylamine, n-pentylamine, n-hexylamine, cyclohexylamine,n-heptylamine, methylcyclohexylamines (for example1-amino-3-methylcylohexane, 1-amino-2-methylcyclohexane, and1-amino-3,3,5-trimethylcyclohexane), n-dodecylamine, 2-aminonorbornane,1-adamantanamine, ethanolamine, methanol, ethanol, n-butanol, n-hexanol,n-octanol, n-decanol, and mixtures thereof. Primary amine terminatorssuch as n-hexylamine, cyclohexylamine, methylcyclohexylamines, andethanolamine are preferred. Diethylenetriamine can also be used at lowlevels in the chain extension step, provided the advantages of theinvention are not compromised.

A variety of additives can also be used in the spandex and the processof the invention, provided they do not detract from its beneficialaspects. Examples include delustrants such as titanium dioxide;stabilizers such as hydrotalcite, mixtures of huntite and hydromagnesite(for example at 0.2 to 0.7 weight percent based on polyurethaneurea),barium sulfate, hindered amine light stabilizers, UV screeners, hinderedphenols, and zinc oxide; dyes and dye enhancers; and the like.

In the process of the invention, the poly(tetramethylene ether) glycolis contacted with 1-isocyanato-4-[(4-isocyanatophenyl)methyl]benzene toform a capped glycol wherein the isocyanate moiety is present at about2.2 to 2.9 weight percent, based on weight of capped glycol. The cappedglycol is mixed with a suitable solvent, for example dimethylformamide,dimethylacetamide, or N-methylpyrrolidone, to form a solution of cappedglycol which is then contacted with a mixture of chain extenderscomprising about 35 to 55 mole percent ethylene diamine, typically about40 to 50 mole percent ethylene diamine, and about 45 to 65 mole percent1,2-propanediamine, typically about 50 to 60 mole percent1,2-propanediamine, to form a polyurethaneurea solution. Thepolyurethaneurea solution can have a falling ball viscosity of about1000 to 4000 poise and can be wet- or dry-spun to form the spandex.

The process can be carried out as batch steps (especially the steps offorming the capped glycol and the polyurethaneurea) or continuously.

In the Examples, the amount of NCO moiety in the capped glycol isreported as a weight percent and was calculated from the followingrelationship:${\%\quad{NCO}} = \frac{100 \times \left( {2 \times {NCO}\quad{fw} \times \left( {C.R.{- 1}} \right)} \right)}{{{glycol}\quad{mw}} + \left( {{C.R.} \times {diisocyanate}\quad{mw}} \right)}$wherein “fw” means formula weight, “mw” means molecular weight, “C.R.”means Capping Ratio (the molar ratio of diisocyanate to polymericglycol), “glycol” means polymeric glycol, and “NCO” refers to theisocyanate moiety, whose formula weight is 42.02.

The viscosity of the polyurethaneurea solution was determined inaccordance with the method of ASTM D1343-69 with a Model DV-8 FallingBall Viscometer (Duratech Corp., Waynesboro, Va.), operated at 40° C.,and is reported in poise.

Intrinsic viscosity (“IV”) of the polyurethaneurea was determined bycomparing the viscosity of a dilute solution of the polymer in DMAc tothat of DMAc itself at 25° C. (“relative viscosity” method) in astandard Cannon-Fenske viscometer tube according to ASTM D2515 and isreported in dl/g. The intrinsic viscosity of the polyurethaneurea ofwhich the spandex is comprised and which is prepared and spun in theprocess of the invention can be about 0.85 to 1.05. The molecularweights of the polyurethaneurea were measured by gel permeationchromatography; its weight average molecular weight (“MW_(w)”) can beabout 80,000 to 105,000, its number average molecular weight (“MW_(n)”)can be about 20,000 to 38,000, and its polydispersity can be about 2.4to 3.6. Higher polyurethaneurea IV and molecular weight can give spandexhaving higher load power and hysteresis, but the effect of changingweight percent NCO and diamine chain extender ratios is substantiallythe same as at lower IV's and molecular weights; it is estimated that anIV change of more than 0.1 would be needed to cause a significant changein hysteresis.

The mechanical properties of the spandex were measured in accordancewith the general method of ASTM D 2731-72. Three filaments, a 2-inch(5-cm) gauge length and a zero-to-300% elongation cycle were used foreach of the measurements. The samples were cycled five times at aconstant elongation rate of 50 cm per minute. Load Power, the stress onthe spandex during initial extension, was measured on the first cycle at100% and 200% extension and is reported in deciNewtons/tex (“dN/tex”).Unload Power, the stress at extensions of 200% and 100% on the fifthunload cycle, is also reported in deciNewtons per tex. Percentelongation at break and tenacity at break were measured on the sixthextension.

In the Tables, “Comp.” indicates a comparison example. The chainextender, other than the amount of 1,2-propanediamine (“PDA”) indicated,was ethylenediamine. All the samples of the invention had a tenacity atbreak of greater than 0.7 dNtex and an elongation-at-break of greaterthan 425%. “LP” means load power, “UP” means unload power, and both arereported in dN/tex. Hysteresis was calculated as the difference betweenload power and unload power and is also reported in dN/tex. “100%”,“200%”, and “300%” refer to the extensions at which the power andhysteresis were measured. In Table I, each error range is for a 95%confidence interval, based on determinations made on 4 wound spandexpackages, each package sampled 6 times.

EXAMPLE 1

Poly(tetramethylene ether) glycol (250.0 grams; Terathane® 2000, aregistered trademark of E. I. du Pont de Nemours and Company) was mixedwith 52.11 grams of 1-isocyanato-4-[(4-isocyanatophenyl)methyl]benzenein a glass reaction kettle. The mixture was heated to 80° C. with aheating mantle and stirred for 90 minutes to make a capped glycol with2.4 wt % NCO (calculated). The capped glycol was dissolved in 572.38grams of dimethylformamide, and 85.51 grams of 2.00 meq/g chain extendersolution (EDA/PDA mole ratio 35/65 in dimethylformamide) and 3.21 gramsof 2.00 meq/g chain terminator solution (ethanolamine indimethylformamide) were added with rapid stirring. The resultingpolyurethaneurea solution had a solids content of 32.0 wt %, based ontotal weight of solution, and the polyurethaneurea's intrinsic viscositywas 0.94 dl/g. An additive slurry was thoroughly mixed into the solutionto achieve in the final fiber 0.5 wt % Methacrol® 2462B (a registeredtrademark of E. I. du Pont de Nemours and Company for a polymer ofbis(4-isocyanatocyclohexyl)methane and 3-t-butyl-3-aza-1,5-pentanediol),1.5 wt % Cyanox® 1790 (a registered trademark of Cytec Industries for2,4,6-tris(2,6-dimethyl-4-t-butyl-3-hydroxybenzyl)isocyanurate), and 10ppm by weight of an anthraquinone brightener. The spinning solution waspumped from a storage tank, metered by a gear pump, heated to about 55°C., and extruded through spinneret holes into a round spinning cellprovided with a co-current flow of hot nitrogen of 405° C. to remove thesolvent. The four filaments were coalesced into one 40 denier (44 dtex)fiber which was passed around a feed roll at 466 m/min, across a finishroll, around a second feed roll at 492 m/min, and wound-up at 548 m/min.Fiber properties are presented in Table I.

EXAMPLE 2

Polymer and fiber were prepared substantially as described in Example 1,except that the % NCO in the capped glycol was increased to 2.8. The IVof the polyurethaneurea in the solution was 0.85, its MW_(n) was 24,200,its MW_(w) was 84,600, and its polydispersity was 3.5. Fiber propertiesare presented in Table I.

COMPARISON EXAMPLE 1

Polymer and fiber were prepared substantially as described in Example 1,except that the % NCO in the capped glycol was increased to 3.2. The IVof the polyurethaneurea in the solution was 1.05, its MW_(w) was100,700, its MW_(n) was 27,000, and its polydispersity was 3.7. Fiberproperties are presented in Table I.

COMPARISON EXAMPLE 2

Polymer and fiber were prepared substantially as described in Example 2,except that the amount of 1,2-propanediamine was increased to 74 molepercent of total chain extender, and the amount of ethylene diamine wascorrespondingly reduced. The IV of the polyurethaneurea in the solutionwas 0.91, its MW_(w) was 98,000, its MW_(n) was 25,000, and itspolydispersity was 3.9. Fiber properties are presented in Table I. TABLEI Example 1 2 Comp. 1 Comp. 2 % NCO 2.4 2.8 3.2 2.8 Capping Ratio 1.691.82 1.95 1.82 Mole % PDA 65 65 65 74 LP @ 100% 0.041 +/− 0.001 0.045+/− 0.001 0.0722 +/− 0.0005 0.051 +/− 0.001 LP @ 200% 0.091 +/− 0.0030.089 +/− 0.004 0.138 +/− 0.002 0.110 +/− 0.003 LP @ 300% 0.21 +/− 0.010.18 +/− 0.01 0.254 +/− 0.004 0.26 +/− 0.01 UP @ 100% 0.0126 +/− 0.001 0.0112 +/− 0.0005 0.0130 +/− 0.0002 0.0133 +/− 0.0002 UP @ 200% 0.019+/− 0.001 0.019 +/− 0.001 0.0209 +/− 0.0003 0.0215 +/− 0.0001 Hysteresis@ 100% 0.029 0.034 0.059 0.037 Hysteresis @ 200% 0.072 0.071 0.117 0.089The data in Table I show that spandex of the invention had unexpectedlylower load power and hysteresis than spandex comprising thepolyurethaneurea reaction product of poly(tetramethylene ether) glycoland high proportions of 1,2-propanediamine and diisocyanate (the latteras indicated by high % NCO in the capped glycol of Comparison Example1).

EXAMPLE 3

Capped glycol having 2.4 weight percent NCO was prepared in a firstwater-jacketed stirred tank from 324.8 kg of poly(tetramethylene ether)glycol having a number average molecular weight of 2029 (Terathane®2000), 68.2 kg of 1-isocyanato-4-[(4-isocyanatophenyl)methyl]benzene,and 0.64 kg of n-butanol. Dimethylformamide was added to dissolve thecapped glycol, the resulting solution was transferred to a secondstirred water-jacketed tank, the first tank was rinsed with additionaldimethylformamide, and the rinse was also transferred to the secondtank, where the polymer content was adjusted to about 36 weight percent.A pigment slurry was mixed into the capped glycol solution in an amountsuch that the subsequent polyurethaneurea solution contained 3 weightpercent titanium dioxide, 0.3 weight percent nonionic dispersant, and 10ppm of an anthraquinone brightener, based on polymer weight. While themixture of solvent, capped glycol, and pigments was stirred at below 10°C., 96 kg of a 35/65 mole/mole mixture of ethylene diamine and1,2-propanediamine chain extenders (7.0 weight percent indimethylformamide) was added until the solution viscosity was about 1650poise. A chain terminator solution (7.43 kg, 30.55 wt % ethanolamine indimethylformamide) was then added, followed by 7.06 kg of 26.91 wt %acetic anhydride in dimethylformamide to ‘neutralize’ the excessethanolamine. The polymer solids level was adjusted to about 32 weightpercent, based on total solution weight, by the addition of moredimethylformamide. The resulting polyurethaneurea solution was thentransferred to a third stirred tank where 13.88 kg of a slurry ofmagnesium stearate, 4.05 kg of a solution of Methacrol® 2462B, and 6.40kg of Cyanox® 1790 were added so that the solution contained 0.28 weightpercent magnesium stearate, 0.5 weight percent Methacrol® 2462B, and 1.5weight percent Cyanox® 1790, based on polyurethaneurea weight. Thesolution was then transferred to an unstirred storage tank from whichsamples were removed at intervals for testing. Over the next 108 hours,during which freshly prepared polyurethaneurea solution was periodicallyadded and solution was continuously removed for fiber spinning, thesolution had shown an advantageously low maximum falling ball viscosityof only 1443 poise, as summarized in Table II and illustrated in FIG. 1.The polymer solution was forced from the storage tank with pressurizednitrogen, preheated to about 45° C., metered by a gear pump, andextruded through spinnerets into a rectangular spinning cell suppliedwith both cross flow and co-current air about 200° C. to remove thesolvent. The filaments were coalesced by false twisting at the bottom ofthe spinning cell into threadlines, supplied with a finish, passedaround a feed roll at 550 m/min and wound up at 480 m/min. Thepolyurethaneurea in the fiber was determined to have an IV of 0.98, aMW_(n) of 36,900, a MW_(w) of 93,300, and a polydispersity of 2.5. Fiberproperties are presented in Table III.

EXAMPLE 4

A polyurethaneurea solution was prepared substantially as described inExample 3, but the capped glycol had 2.8 weight percent NCO. During 105hours in the storage tank, during which freshly preparedpolyurethaneurea solution was periodically added and solution wascontinuously removed for fiber spinning, the solution had shown amaximum falling ball viscosity of only 1534 poise, as summarized inTable II and illustrated in FIG. 1. The IV of the polyurethaneurea inthe fiber was 1.00. Fiber properties are presented in Table III.

COMPARISON EXAMPLE 3

A polyurethaneurea solution was prepared substantially as described inExample 3, but the capped glycol had 2.4 weight percent NCO, the moleratio of ethylene diamine to 1,2-propanediamine in the chain extendermixture was 60/40. After 81 hours in the storage tank, during whichfreshly prepared polyurethaneurea solution was periodically added andsolution was continuously removed for fiber spinning, the falling ballviscosity had risen to an unsatisfactory 4626 poise, as summarized inTable II and illustrated in FIG. 1. The IV of the polyurethaneurea inthe fiber was 1.00. Fiber properties are presented in Table III. TABLEII Example 3 4 Comp. 3 % NCO 2.4 2.8 2.4 Mole % PDA 65 65 40 Time, hrs108 105 81 Maximum poise 1443 1534 4626

The data in Table II show that the solution viscosity remainedsatisfactorily low for polyurethaneurea reaction product ofpoly(tetramethylene ether) glycol,1-isocyanato-4-[(4-isocyanatophenyl)methyl]benzene, and a 35/65 moleratio of ethylene diamine and 1,2-propanediamine chain extenders butrose to unsatisfactorily high levels when the amount of1,2-propanediamine was reduced to 40 mole percent. Interpolation of thedata for Example 3 and Comparison Example 3 shows that a stillsatisfactory maximum of about 4000 poise would be reached at about 45mole percent 1,2-propanediamine. TABLE III Example 3 4 Comp. 3 % NCO 2.42.8 2.4 Mole % PDA 65 65 40 LP @ 100% 0.0503 +/− 0.0002 0.0573 +/−0.0003 0.0503 +/− 0.0002 LP @ 200% 0.1183 +/− 0.0009  0.132 +/− 0.00150.1101 +/− 0.0007 LP @ 300% 0.207 +/− 0.002 0.224 +/− 0.002 0.162 +/−0.002 UP @ 100% 0.0142 +/− 0.0001 0.0138 +/− 0.0002 0.0132 +/− 0.0001 UP@ 200% 0.0229 +/− 0.0001 0.0232 +/− 0.0003 0.0204 +/− 0.0001 Hysteresis@ 100% 0.036 0.044 0.037 Hysteresis @ 200% 0.095 0.109 0.090Examination of the data in Table III shows that the unload power ofComparison Example 3 is undesirably low, compared to Examples 3 and 4.The differences in fiber properties between those of Table I and TableIII are believed to be due to differences in spinning conditions.

1-4. (canceled)
 5. A process for making spandex comprising the steps of:a) providing poly(tetramethylene ether) glycol; b) providing1-isocyanato-4-[(4-isocyanatophenyl)methyl]benzene; c) contacting thepoly(tetramethylene ether) glycol and the1-isocyanato-4-[(4-isocyanatophenyl)methyl]benzene to form a cappedglycol wherein the weight percent of isocyanate moiety is from about 2.2to about 2.9 based upon the weight of the capped glycol; d) providing asolvent; e) mixing the solvent and the capped glycol to form a cappedglycol solution; f) contacting the capped glycol solution and a mixtureof chain extenders comprising: from about 35 mole percent ethylenediamine; to about 55 mole percent ethylene diamine; and from about 45mole percent 1,2-propanediamine; to about 65 mole percent1,2-propanediamine to form a polyurethaneurea solution; and g) spinningthe polyurethaneurea solution to form the spandex.
 6. The process ofclaim 5 wherein steps c) and f) are carried out as batch steps and thefalling ball viscosity of the polyurethaneurea solution is about 1000 to4000 poise.
 7. The process of claim 5 wherein the solvent isdimethylformamide and the poly(tetramethylene ether) glycol issubstantially free of diols having molecular weight of less than 250daltons.
 8. The process of claim 5 wherein the mixture of chainextenders comprises at least about 40 mole percent ethylene diamine, atmost about 50 mole percent ethylene diamine, at least about 50 molepercent 1,2-propanediamine, and at most about 60 mole percent1,2-propanediamine.
 9. The process of claim 5 wherein the mixture ofchain extenders of step (f) further comprises at least one primary aminechain terminator.
 10. (canceled)